Balanced draft and flash wall for kilns



Sept. 19, 1939. L. R. ROBINSON v BALANCED DRAFT AND FLASH WALL FOR KILNS Filed May- 7, 1936 ATTORNEY.

Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE Lawrence R. Robinson, Zelienople, Pa., assignor to United Combustion Corporation, a corporation of Delaware Application May 7, 1936, Serial No. 78,340

8 Claims.

This invention relates to kilns and particularly to kilns for burning ceramic products.

One of the principal objects of the present invention is to introduce heating media initially in a more uniformly distributed condition into the kiln from a plurality of separate sources of heat so as to effect a more uniform application of the heat to the articles being treated therein.

Another object is to efiect more nearly a bal- 10 ance between the delivery of the sources of heat automatically so that excessive heating at any source is eliminated and the structural parts of the kiln itself are protected.

A more specific object is to cause a uniform flow 35 of the products from the various heating sources onto the articles being treated.

Another specific object is to provide a balanced flash wall in a kiln for distributing the heating media more uniformly preparatory to their discharge onto the articles being treated in the kiln.

Other objects and advantages will become apparent from the following specification, wherein reference is made to the drawing in which Fig. 1 is a fragmentary horizontal sectional view of a kiln embodying the principles of the present invention and is taken on a plane indicated by the line l-l in Fig. 2;

Fig. 2 is a fragmentary developed elevation of the interior of the kiln, as viewed from the line 2--2 in Fig. 1, part thereof being shown in section; and

Figs. 3 and 4 are respectively fragmentary sectional views of the kiln taken on planes indicated by the lines 3-3 and 44 respectively of Fig. 2.

For the purposes of illustration, the present invention will be described in connection with the usual beehive kiln for burning ceramic products, its application to other form of kilns and for other purposes being readily apparent therefrom.

Referring to the drawing, the kiln comprises a circumferential outer wall I which is preferably of brick or suitable refractory material and which supports at the top the usual top wall or dome ceiling, not shown. The usual stack, connected through the floor of the kiln with the interior thereof to effect a down draft therethrough, is also provided, though not shown herein.

The wall I has a series of peripherally spaced firing passages 2 opening into the interior of the :31) kiln, as better illustrated in Figs. 2 and 4. The passages 2 are open to the outside of the kiln for receiving coal or other fuel and are provided with .the usual ash passages 3 adjacent the bottom and suitable air and observation ports 4 and 5 re spectively.

customarily in such structures, short semi-cy lindrical flash walls are provided immediately within the kiln in alignment with the firing passages 2, respectively, each of these flash walls joining the wall I a short distance to each side 5 of the associated firing passage and opening into the kiln cavity only at the upper limit of the flash wall, thus providing a series of internal flues respective to the passages 2. v

The structure thus far described is that usually provided'in kilns of this type. In such structures the products of combustion tend to localize in their passage over the upper edge of the semicylindrical flash walls with the result that overheating adjacent the firing passages results unless the entire kiln is brought up to the required temperature at a slow rate for preventing such localized overheating. Again, due to outside wind conditions and the like, and the differences in firing of the various firing passages, the rate of combustion of the fuel in the different firing passages varies widely, thus augmenting the overheating effects adjacent some passages and causing underburning and underheating adjacent other passages.

In the present invention these isolated Wall flash structures are dispensed with and an inner peripherally continuous flash wall 6 of refractory material is provided, the flash wall 6 being in inwardly spaced relation from the outer wall I so as to define therewith a free, circumferential passage, open at the top limit of the flash wall to permit the flow of products of combustion thereover and onto the articles within the kiln, as indicated by the arrows 1. Even with the flash wall 6 there is a tendency for the heating media to localize near the zone of the associated firing passage 2.

For eliminating or reducing theselocalizing effects, the wall 6, instead of being of uniform height at all portions is higher in the zone of the firing passages, as indicated at 6a, than at points remote from the passages. The higher portions 6a are preferably coextensive peripherally with the associated firing passages. From the flash wall portions 6a, the upper limit of the wall slopes downwardly, as indicated at 617, to intermediate low level portions So which are substantially midway between the firing passages 2. The low level portions 60, joining adjacent downwardly sloping portions 6b, are preferably horizontal. Thus a wall of alternate crests and troughs is provided, the crests being arranged adjacent the firing portions and the troughs being remote therefrom.

Between the flash wall 6 and the outer wall I and extending from the lateral limits of the firing passages, are upwardly sloping deflecting walls 8 which are substantially at the level of the fire bed. adjacent the firing passages 2 and slope gradually upwardly to the upper limit of the wall portion 60. In the form illustrated, these deflecting walls are built of refractory blocks which are offset in step formation, the steps, in turn, being filled with said or suitable refractory material so as to provide a more even sloping surface. As a result of the downward sloping of the upper limit of the flash wall '5 and the upward sloping of the deflecting walls 8, the passages for products of combustion or heating media from each firing passage 2 are gradually contracted in the .direction of flow of the media toward the discharge portions thereof to provide more uniform distribution. The discharge of such media is over the upper limit of the wall 6 of which all portions are more nearly the same distance from the center of the fire bed of the associated passage so that more equal initial distribution of the media around the kiln preparatory to discharge thereinto is effected. If desired, the top limit of the wall 5 may approximate more nearly the theoretically proper wall of which the top limit is so configured that all points are substantially equally spaced from the fire bed.

Even with this flash wall there is a tendency for less of the products to reach the portions 6c of the wall than reach the portions Ba and 6b, as the heating media rise rapidly due to their intense heat. Consequently, the walls 8 are provided with passages 9 which extend entirely therethrough parallel to the flash wall 6 and are positioned at substantially the same elevation as the fire bed in the firing passages 2. Each of the passages 9 are fully open at both ends through the ends of the walls 8 so as to provide free communication between the firing passages 2.

In vertical alignment with the portions 60 of the flash wall 6 are enlarged discharge passages in which are in free communication with the passages 9, as a result of which heating media from both adjacent firing passages may pass comparatively freely to the intermediate associated discharge passage IE3, as indicated by the arrows 1a. Necessarily the walls 6 in alignment with the firing passages are heated to a Very high deree comparatively rapidly, but due to the passages 9 and discharge passages ID, the heating is more uniformly distributed along the wall 6 and the disproportionate heating of the wall 6 adjacent the passages 2 is greatly reduced.

Again, the discharge of products of combustion from the passages l0 tends to compensate for the less amount of the products passing over the portion 60 of the wall 6. As a result a more uniform initial introduction of heating media into the kiln is provided and more uniform flow of the media through the kiln to the stack results.

As mentioned heretofore, there is a tendency for the firing and resultant rates of combustion to vary in the different passages 2. Due to the passages 9 and In, any excessive combustion in one passage with resultant greater intensity of heating is not isolated and rendered effective only adjacent the passage in which it occurs as the excess heating media can flow rapidly through the passages 9, distributing heat during their passage therethrough and venting at the passages I0 which are near the firing passages 2 in which less intense combustion is taking place, or venting into such other firing passages, Thus localized currents in the kiln of excessively heated heating media are reduced, the expansive pressure of the media and distribution thereof being balanced through the passages 9 and Ill preparatory to entrance onto the articles in the kiln.

Not only does this effect a more nearly even distribution of heating media but also permits a rapid removal of the heating media from the firing passages with a consequent reduction in the damage that might otherwise be caused. Even with the flash wall provided with crests 6a and troughs 60 if no passages 9 and I!) are pro- Vided, there is a tendency for the flame to be come more concentrated, adjacent the crest portions 5a with resultant overheating of adjacent articles in the kiln, and to become less effective adjacent the trough portions 60. These effects are evidenced by flames which though spreading fan shape from the crest portions 6a, parallel to the flash wall, as is desired, are nevertheless separate from each other and form a series of flames instead of a continuous flame. This action is due largely to the fact that the kiln is of the downdraft type, and the heating media rise very rapidly adjacent the firing passages and tend to localize the flow through the kiln. This rise is so rapid relative to the draft that the heating media pass over the wall adjacent the firing passages before the media can travel to the troughs of the flash wall under the influence of the downdraft. With the passages 9 and If however, part of the media may pass from the firing passages to the passages 10, under the influence of the downdraft, thus concurrently relieving the draft effect at the crest portions and causing an appreciable localization of the draft adjacent the trough portions 60. As a result, the downdraft induces a greater flow toward the troughs and the flames from the firing passages spread more and merge at their margins preparatory to passage over the flash wall. These phenomena result in a continuous unbroken flame along the flash wall. Also, due to the introduction of media at the passages l0, adequate heat is provided for the lower strata of articles being burned at the points most remote from the firing passages whereas, in the usual downdraft kilns, the lower strata most midway between the passages can be burned adequately only by very cautious and slow firing or overburning of the upper strata adjacent the firing passages results.

Necessarily, if a heavy wind is blowing on one side of the kiln, causing a very reduced atmospheric pressure at the opposite side, the flow of gases through the passages 9 will be augmented and though some heat may be lost, nevertheless a large portion thereof will be carried around toward the leeward portion of the kiln, heating the walls and partially discharging during its travel, with a resultant better distribution of the heat to the articles being fired. All parts of the kiln exposed to excessive heat are preferably of the usual refractory materials capable of withstanding, without undue fusion, the heats towhich subjected. For the purposes of illustration, the more heat resistant refractory materials have been shown on the surfaces exposed to the greatest heat.

For the purposes of illustration the present invention has been described in connection with the usual ceramic kiln of the beehive type which is fired by coal and other solid fuels. It is to be understood, however, that the same is meant to include other types of kilns and instead of the usual coal firing passages the kilns may be fired at the passages with other types of fuels, such, for example, as gas, oil and the like.

Again, it should be noted that the word kiln is used in a generic sense to include all types of furnace structures wherein articles are to be heat treated and is not meant merely to refer to the burning of ceramic products. Instead the word kiln is meant to include annealing furnaces for metal products, drying furnaces and the like in which uniform distribution of the heat and uniform initial application thereof to articles being burned or heat treated is desirable.

Having thus described my invention, I claim:

1. In a kiln for the purposes described, including a ceiling, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall within the kiln and spaced inwardly from the outer wall and extending therealong past the passages and terminating in spaced relation below the ceiling of the kiln, and said flash wall being of greater height at the zones adjacent the firing passages than at the zones between the passages.

2. In a kiln for the purposes described, including a ceiling, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall within the kiln and spaced inwardly from the outer wall and extending continuously therealong past said passages and terminating in spaced relation below the ceiling of the kiln, said flash wall being of greater height adjacent the firing passages than between the passages and sloping gradually downwardly from the higher portions to the lower portions.

3. In a kiln for the purposes described, including a ceiling, an outer wall and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall within the kiln and spaced inwardly from the outer wall and extending continuously therealong and terminating in spaced relation below the ceiling of the kiln for admitting products of combustion from the firing passages thereover into a material treating zone of the kiln, the upper limit of said flash wall being of different elevations for causing more nearly equal distances of travel of all products from the firing passages over the upper limit of the flash wall preparatory to reaching said upper limit.

4. In a kiln for the purposes described, including a top wall, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall within the kiln and spaced inwardly from the outer wall and extending continuously therealong and terminating in spaced relation below the top wall of the kiln, said flash wall being of greater height at the zone of the firing passages than at the zone between the passages and sloping downwardly from the higher portions to the lower portions, baffle walls between the flash wall and said outer wall, said baflle walls being disposed between adjacent firing passages and sloping upwardly from adjacent the associated firing passages to the zone of the lower portion of said flash wall, whereby continuous passages are formed for passage of a more uniform distribution of products of combustion from the firing passages along the flash wall preparatory to discharge of said products over said wall into a material receiving portion of the kiln.

5. In a kiln for the purposes described, in-

cluding a top wall, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash Wall within the kiln and spaced from the outer wall and extending therealong and past the firing passages and terminating in spaced relation below the top wall of the kiln, baffle walls between the flash wall and said outer wall, said bafile walls being disposed between adjacent firing passages and sloping upwardly from adjacent the firing passages to a zone midway therebetween for effecting better distribution of the products from the firing passages along the flash wall preparatory to the discharge thereof over the flash wall.

6. In a kiln for the purposes described, including a top wall, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall Within the kiln and spaced from the outer wall and extending continuously therealong and terminating in spaced relation below the top wall of the kiln, said flash wall being of greater height at zones adjacent the firing passages than at zones be tween the passages and sloping downwardly from the higher portions to the lower portions, and bafile walls between the flash wall and said outer wall, said b-aflle walls being disposed one between each pair of adjacent firing passages and sloping upwardly from adjacent the firing passages to a zone midway therebetween and terminating at their upper limit close to the upper limit of the lower portions of said flash Wall, said baflle walls having passages therein extending longitudinally of the flash wall from each firing passage to the adjacent firing passage, whereby a continuous passage is formed for passage of products of combustion from each firing passage along the flash wall, and ports in the flash wall and positioned longitudinally thereof between the zones of the firing passages and discharging into the interior of the kiln.

7. In a kiln for the purposes described, including a top wall, an outer wall, and a plurality of firing passages therein and spaced apart from each other therealong, a flash wall within the kiln and spaced from the outer wall and extending continuously therealong and terminating in spaced relation below the top wall of the kiln, said flash wall being of greater height at zones adjacent the firing passages than at zones between the passages and sloping downwardly from the higher portions to the lower portions, and ports in the flash wall and positioned longitudinally thereof between the zones of the firing passages and discharging into the interior of the kiln.

8. In a kiln for the purposes described, including a top wall, an outer wall having a plurality of firing passages spaced from each other therealong, a flash wall within the kiln and spaced from the outer wall thereof and extending continuously therealong and terminating in spaced relation below the top wall of the kiln and defining with the outer wall a continuous passage for products of combustion from the firing pas sages along the flash wall, said flash wall being of greater height at the zones adjacent the firing passages than at the zones between the passages, and ports in the flash wall in communication with said continuous passage and positioned longitudinally of the flash wall substantially midway between the zonesv of the firing passages and discharging into the interior of the kiln.

LAWRENCE R. ROBINSON. 

